An inner ideal of an associative ring R is an additive subgroup V of R such that [V[ VR]] C I/. This paper examines the inner ideal structure of semiprime associative rings and of the skew elements of prime rings with involution. The results are analogous to those obtained by Herstein, Baxter, and Erickson for the Lie ideals of these rings. In the special case when R is a simple Artinian ring with center 2 of characteristic not 2 or 3, and of dimension greater than 16 over 2, then [RR]/2 n [RR] is a simple Lie algebra over Z satisfying both the ascending and descending chain conditions on inner ideals. Every inner ideal has the form eRf for e, f idempotents of R such that fe = 0. Moreover, if * is an involution on R and if K denotes the skew elements relative to *, then [AX]/2 n [KK] also satisfies both chain conditions on inner ideals. Every inner ideal of this algebra can be written as eKe* for some idempotent e of R such that e*e = 0. The motivation to study inner ideals in Lie algebras can be found in a recent paper [3] by the author. The inner ideals of a Lie algebra are closely related to the ad-nilpotent elements, and certain restrictions on the adnilpotent elements yield an elementary criterion for distinguishing the nonclassical from classical simple Lie algebras over algebraically closed fields of characteristic p > 5. In what follows R is a noncommutative, associative ring. Say R is n-torsion free where n is a positive integer if, in R, nx = 0 implies x = 0. Let 2 denote the center of R, and given elements a, b in R, let [ab] = ab ~ ba. Then 2 {a E R 1 [ab] = 0 for all b in Ii}. Alternatively, given any a in R if D,,(r) = [ar], then 2 = {a E R / D, = O}. For subsets A, B of R use [AB]
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